It was narrated that Anas bin Malik said: "A funeral (procession) passed by the Prophet and they praised (the deceased) and spoke well of him. He said: '(Paradise is) guaranteed for him.' Then another funeral passed by and they spoke badly of him, and he (the Prophet P.B.U.H) said: '(Hell is) guaranteed for him.' It was said: '0 Messenger of Allah, you said that (Paradise was) guaranteed for this one and that (Hell was) guaranteed for the
other one.' He said: 'It is the testimony of the people, and the believers are the witnesses of Allah on earth.''' (Sahih)